1. Field of the Invention
The present invention relates to safety devices for persons at elevated locations and, more particularly, relates to an improved device for safely supporting a workman tied off with a lanyard and safety harness to a cable, while allowing the lanyard to be easily and quickly moved along the cable and past a cable support.
2. Description of the Background
Government and industry regulations require that personnel working at elevated positions be "tied off" for safety. One popular type of safety system employs a fall restraint cable permanently secured at each end to a building structure, pipeway rack, etc. A tether line has a conventional safety hook at one end, and a safety harness at the other end worn by the worker. The worker attaches the safety hook (and thus himself) to the fall restraint cable, which is stretched taunt and tied off between supports. As a worker moves in a direction along the cable, the lanyard or safety hook slides over the cable.
In order to limit the distance a worker can fall, regulations limit the length of the tether, and also require the fall restraint cable to be supported at regular intervals, e.g., at least every 20 feet. These intermediate cable supports are typically a short section of pipe which is secured to the structure, with the cable passing through the section of pipe. The problem exists, however, that the lanyard cannot pass by this intermediate support. Either the worker fails to tie off when switching the lanyard from one side of the intermediate support to the other side (a violation of regulations), or he must carry two lanyards and connect the second lanyard to one side of the intermediate support before unhooking the first lanyard from the other side of the intermediate support.
Other prior art safety devices have been devised which do not utilize the fall restraint cable as the primary support for restraining the worker if he should fall. U.S. Pat. No. 3,860,089 discloses an elongated plastic tube with a continuous entrance slot for receiving a block connected to a safety line. U.S. Pat. No. 4,721,182 teaches a guide rail supported by fasteners. A safety rod connects the worker to the guide rail through a closable end piece. Neither of these patents utilize a conventional taunt fall restraint cable, which has become widely accepted in the industry.
U.S. Pat. No. 3,193,050 discloses a device for securing a safety line for a workman operating at elevated places. The device disclosed in this patent includes a spring hook ring which passes by a plate and bracket member. The spring hook ring must be passed through an opening in the plate, and positioned through a series of movements to pass by the plate and the shaft. These complicated movements greatly detract form the desired simplicity of the intermediate support, and accordingly the device as taunt by this patent has not been widely accepted.
U.S. Pat. No. 4,699,245 also discloses a safety system which utilizes a taunt cable and intermediate supports. The intermediate supports are designed for fastening to a fixed wall or other fixed member in the position as shown in the figures. More importantly, the intermediate support includes a disk which rotates about an axis. Intermediate supports with movable components, as disclosed in the '245 patent, are not favored in the safety industry, in part because such supports are more likely to fail than a support with no moving parts. Debris, corrosion, and other elements may prohibit the movable components from operating, although this problem cannot be easily detected before the workman tries to pass the lanyard along the fall restraint cable past the intermediate support. If the disk as shown in the '245 patent becomes locked or seized to the shaft, the workman is not likely to repair the intermediate support, but rather is more inclined to unhook his lanyard from one side of the intermediate support and then rehook his lanyard on the other side of the intermediate support. This detachment and reattachment of the lanyard violates the one-hundred percent tie off regulation, and obviously subjects the worker to a high safety risk if he should slip while the lanyard is disconnected from the fall restraint cable.
U.S. Pat. No. 4,790,410 discloses another type of safety system for connecting a workman to a fall restraint cable. A coupling device which includes a helical longitudinal slot is passed through a support secured to the fall restraint cable. An arm may be secured to the coupling, and safety line or tether is attached at one end to the arm. The intermediate support includes a head portion with tapered ends, and a post interconnects a fixing plate to the head portion. A workman rotates the coupling device and arm to pass the post through the helical slot, thereby allowing the coupling device to pass from one side to the other of the intermediate support. Alternatively, a slotted tube having a helical passageway may be secured to the building, and a coupling component including a tubular head portion receives the cable and passes through the helical slot in the tube. The device as disclosed in the '410 patent requires that one component rotate 360.degree. about the axis of the cable to pass by the intermediate support, which is a significant disadvantage of the device. Also, the device requires both a specially fabricated and expensive intermediate support and a specially fabricated member for securing the conventional hook at the end of the tether to the safety cable. Accordingly, this device has the disadvantage of both an expensive intermediate support and a special device which must be used to secure the safety cable to the tether hook.
Soviet Union Disclosure No. 1178866 teaches intermediate supports for a safety or fall restraint cable. The intermediate support is a section of casing with a sinusoidal groove having an axis of symmetry in the plane of the axis of the support. A significant although not readily apparent disadvantage of this device, which is also a disadvantage of the prior art intermediate supports comprising short sections of pipe discussed earlier, is that birds tend to build nests within the short pipe section. Again, the safety hook must be weaved through the sinusoidal groove in the tube, and can become stuck, especially if nests or other debris are contained within the section of pipe. French Patent No. 2615-742 discloses a similar intermediate support fabricated from a rectangular housing rather than a section of pipe, and includes an inverted V-shaped slot rather than a sinusoidal groove. Soviet Union Disclosure No. 1,178,855 discloses a support for a safety cable which uses a wheel having radially outward spokes for supporting the cable. This device is expensive to manufacture, and requires moving parts which must rotate about an axis. Accordingly, this device has many of the disadvantages discussed above with respect to U.S. Pat. No. 4,699,245.
The disadvantages of the prior art are overcome by the present invention, and an improved fall restraint cable support and method are hereinafter disclosed suitable for providing intermediate support to a safety cable while allowing a conventional hook, ring or clasp at the end of a tether to easily and quickly pass by the intermediate support.